Vulcanizable rubber mixtures

ABSTRACT

Vulcanizable rubber mixtures having improved room temperature hardness containing 2-20% by weight, calculated on the rubber, of a polyoctenamer or polydodecenamer.

United States Patent Nordsiek et al.

VULCANIZABLE RUBBER MIXTURES Inventors: Karl-Heinz Nordsiek; Roland Streck, both of Mar], Germany Assignee: Chemische Werke Hals Aktiengesellschaft, Marl, Germany Filed: June 22, 1972 Appl. No.: 265,167

Foreign Application Priority Data June 24, 1971 Germany 2131354 US. Cl. 260/4 R, 152/357, 260/5, 260/23 R, 260/42, 260/32, 260/23.7 M, 260/23.7 R, 260/33.6 AQ, 260/79.5 C, 260/79.5 B, 260/887, 260/890, 260/897 R Int. Cl C08d 9/08, C086 9/ l4, C08c 9/04 June 11, 1974 3,732,338 5/1973 Theisen eta]. 260/93.l

Primary Examiner--Wilbert J. Briggs, Sr. Attorney, Agent, or FirmMillen, Raptes & White [5 7] ABSTRACT Vulcanizable rubber mixtures having improved room temperature hardness containing 220% by weight,

calculated on the rubber, of a polyoctenamer or polydodecenamer.

14 Claims, N0 Drawings VULCANIZABLE RUBBER MIXTURES BACKGROUND OF THE INVENTION This invention relates to vulcanizable rubber mixtures, more particularly vulcanizable mixture of elastomeric and thermoplastic polymers of high thermoplasticity and improved green-strength, to a method for improving the hardness of unvulcanized rubber mixtures and to articles of manufacture produced therefrom.

The synthetic vulcanizable rubbers normally exhibit too low green-strength. They do not possess the stamina of natural rubbers, which frequently results in problems in the processing operation for the production of elastomeric products. Furthermore, along with the requirement that the pre-formed, unvulcanized articles be stable, increased mixture hardness at room temperature is often desirable.

Thus, it is an absolute prerequisite for a large number of processing operations that the unvulcanized rubber mixture have a high degree of thermoplasticity. This means that the hardness thereof, for example, defohardness (defo) measured according to German Industrial Standard DIN 53 514 at 20 C. should be relatively high, but at the processing temperature, which is normally above 80 C., should be within the normal range or therebelow. In this way, processing operations are simplified on the one hand and on the other hand, the article produced therefrom, e.g., a tire or a part thereof, alters its shape at most to an insubstantial extent during the intermediate storage until the shape is set by vulcanization.

In principle, this objective can be attained by adding thermoplastic polymers to the vulcanization mixture, whose fusion temperature and/or glass point are between the storage temperature and the processing temperature. Examples of such polymers are polystyrene and styrene-enriched butadiene-styrene copolymers. However, these polymers impair the dynamic properties of the vulcanizates, so that such mixtures are unsuitable for the production of articles subjected to strongly varying mechanical stresses, e.g., automobile tires.

To a certain extent, these undesired consequences can be avoided by the addition of polyethylene. However, besides the high softening point of such polymers, because there is no possibility of covulcanization, polyethylenes also do not provide a successful solution of the problem described above.

It is an object of the present invention to improve the disadvantages of the above-described state of the art, i.e., to provide vulcanizable rubber mixtures which, in the unvulcanized condition, exhibit the desired pronounced thermoplasticity without adversely affecting the dynamic properties of vulcanizates produced therefrom.

SUMMARY OF THE INVENTION The vulcanizable elastomers of this invention contain 2-20 percent by weight, preferably 5-15 percent by weight, based on the elastomer, or a polyoctenamer, a polydodecenamer, or a mixture thereof, whose double bonds are more than 60 percent in the transconfiguration and have a reduced viscosity at 135 C., of 0.2-3.0 dL/g.

DETAILED DISCUSSION The polyalkenamers employed on the compositions of this invention, i.e., polyoctenamer and polydodecenamer, can be produced in a conventional manner from cyclooctene and cyclododecene, respectively, by ring-opening polymerization in solution in the presence of a mixed catalyst containing a compound of a metal of Sub-groups 5 through 7 and a metal of Main Groups 1 through 4 of the Periodic Table, or a compound thereof, as well as optional additional activators.

The proportion of double bonds in the transconfiguration in these polyalkenamers must be more than 60 percent, preferably between and percent, and they must have a reduced specific viscosity of 0.2 3.0 dl./g. at C. (in Decalin decahydronaphthalene). For illustrative methods of preparing such polymers, see, e.g., Scott, Calderon, Ofstead, Judy and Ward, Rubber Chemistry and Technology, 44

(1971), 1341 and the references cited therein.

Vulcanizable rubbers whose processing properties can be improved include all natural and synthetic polymers and mixtures thereof which are elastomers, e.g., natural rubbers, synthetic rubbery polymers, including homoand copolymers of butadiene, isoprene and 2- chlorobutadiene, e.g., BR (polybutadiene rubber), IR (polyisoprene rubber), SBR (styrene-butadiene rubber), NBR (nitrile-butadiene rubber), CR (polychloroprene rubber), and copolymers of at least two a -olefins and optionally one more multiens, i.e., polyunsaturated olefins, e.g., EPM (ethylene-propylene rubber) and EPDM (ethylene-propylene-diene rubber).

The exact amount of polyalkenamer employed in the compositions of this invention depend on the hardness of the unmodified elastomer and desired hardness of the unvulcanized mixture at room temperature. Generally, about 2-20 percent, preferably 5-15 percent, by weight of polyoctenamer and/or polydodecenamer, calculated on the elastomer, is employed. For example, to double the defo hardness of the finished mixture, about 10 percent by weight, calculated on the elastomer, of the trans-polyoctenamer or -polydodecenamer, is normally sufficient.

The herein-described auxiliary agents can be added to conventional rubber pre-vulcanizate mixtures in customary processing assemblies used in the rubber industry, with the prerequisite that a processing temperature of greater than 70 C. is employed during this treatment. Normally, the mixing step can be performed, without special operating procedures, simultaneously with the incorporation of fillers and other components during the production of the basic mixture by a rolling mill or internal mixer.

Without any limitation, all types of active and inactive fillers customary in the rubber industry can be present in the vulcanizable rubber compositions of this invention, e.g., carbon blacks, silicic acid, kaolin, etc., optionally with the simultaneous utilization of plasticizers, especially aromatic, naphthenic, and paraffinic mineral oils. It is, of course, possible to employ the conventional adjuvants, e.g., anti-aging agents and crosslinking agents, for the production of specific vulcanizates.

The thus-prepared mixtures exhibit advantageous behavior during the further processing within the scope of the preparation of shaped articles of manufacture, due to their improved flow properties. The considerable increase in tensile strength at room temperature in the unvulcanized compositions which results by the incorporation of the polyalkenamer is of special advantage, so that the finishing steps during the production of rubspecial measures or devices. Using conventional vulcanization systems, practically unchanged heating periods result, based on the temperature customarily con sidered an optimum for the respective mixture.

by Wt.

ber goods are favorably affected. I v7 Without further elaboration, it is believed that one Of paramount Significance is the use of the additives sk lled in the art can. using the preceding description. to be employed according to this invention in the storunhzeflw Present to fulles! exlenlage of pre-formed unvulcanized articles or blanks until followmg Preferred Speclfic eelbodlmems are {herevulcanizafion The thuyobtained extraordinary prolom fore to be construed as merely illustrative. and not limgation of the minimum Storage Stability ensures high 10 name of the remamder of the d1sclosure 1n any way dimensional stability and thus substantially precludes whalsoever' troublesome problems arising in the course of the man- EXAMPLE 1 "faetuflng Processes P f e Bering Using an internal mixer (type GK 2; shell temperathe p f e articles where"! a high dimensional l 5 ture 50 C.; speed of front rotor 50 rpm) additives accuracy q l Such as, example the me customarily employed for the production of vulcanif belted "Yes, the vuleamzable eomposltlens 0f zates were incorporated into known rubbers. The mixth1s lnvent lon can advantag c l y be P y q t0 ing time was 5 minutes. The temperature of the matethe ig q msns o g ws ab y t ra QE mQW rial upon discharge varied between 115 and 140 c.

The addition of the polyoctenamer and/or polydo- The thus-produced basic unvulcanized mixture condecenamer during the processing of rubber mixtures tained, in each case, 50 parts by weight of HAF (high with high proportions of plasticizer and also to rubbers abrasion furnace) carbon black, 8 parts by weight of having relatively low molecular weights is particularly processing oil with a high content of aromatics, 3 parts advantageous. Thus, advantages are clearly apparent by weight of zinc oxide, 2 parts by weight of stearic wherever especially soft rubbery pre-polymerizates, acid, and 1 part by weight of a discoloring anti-aging e.g., those having a deformation hardness (DIN 535 l4) agent, respectively, based on 100 parts by weight of the at 20 C. in unmodified form of less than 6,000, less rubber. The tensile strength and the thermoplasticity, than 4,000, preferably 2,0004,000, pass through the measured according to defo (DIN 53 514), of the unmanufacturing procedure, which provide savings and vulcanized samples were measured and compared to facilitate many processing steps during the mixing and these same properties of a second series of these mixshaping which usually involve considerable difficulties tures which additionally contained 10 parts by weight, because of the lack of dimensional stability due to inbased on the rubber content, of a polydodecenamer creased flow tendency. Here, the additives to be used having a trans-1,4-content of 75 percent and a RSV- according to this invention permits fully exploiting the value of 0.8 dl./g. The results are set forth in Table l. economical advantages having mixtures of low- In addition to the increase in raw tensile strength which viscosity during processing, i.e., deformation hardness is, in part, very pronounced, a surprisingly strongly disat 20 C. is usually increased at least more than tinct increase in the defo hardness at 20 C. is observed 4,000, e.g., about 5,000-9,000. in each sample to which was added the polydodece- The cross-linking vulcanization reaction can be connamer. Plasticity in the processing temperature range ducted in presses, autoclaves, etc., and does not require 40 is unchanged or somewhat lower.

TABLE 1 RUBBER POLY- RAW DEFO ACC. to DIN 53 514 DODECEN- TENSILE ELONGA- i AMER STRENGTH TION 20C. C.

kg./cm

la Natural Rubber lb Sheets Defo 1200 None 4.0 276 3000/25 680/! I do. 10 Parts 10.1 304 7000/30 580/11 by Wt.

lt' Synthetic Poly- ISOPICHC (Ziegler Type) None 1.8 I76 2000/9 500/5 Commercial Product Natsyn" 2200 Id do. 10 Parts 3.3 190 4600/15 400/5 by Wt.

le Synthetic Polyisoprene Li Type, Commer- None 1.7 81 2200/l l 600/5 cial Product Cariflex" IR 305 If do. 10 Parts 29 60 4800/15 600/6 hy Wt.

lg 8BR 1500 None 4.1 5400/23 1400/22 1/1 SHR 1500 10 Parts 5.5 119 11000/24 11110/23 TABLE l-Continued RUBBER POLY- K/LW. .em Aug-.19 DID/.53 4

DODECEN- IENSILE ELQblQA- AMER STRENGTH 'flON 7% 20 C. 80 C.

ltg/cm li cis-l.4-Poly butadiene Commercial None 2.6 536 2700/32 1700/26 Product "Buna" CB l0 1] do. Parts 3.9 317 4300/35 1500/27 by Wt.

EXAMPLE 2 EXAMPLE 3 Following the procedure of Example 1, elastomer To the following elastomeric mixture, which is suitmixtures were once again prepared, employing various able, for example, for the production of articles subtypes of rubber. The proportion of filler in this case was 70 parts by weight of HAF carbon black, and the proportion of plasticizer was 40 parts by weight of aromatic extender oil. in a second series of mixtures 15 parts by weight, based on the rubber, of a polyoctenamer with a trans-1,4-content of 85% and a RSV- value of 1.1 d1./g. was admixed to improve the raw tensile strength and thermoplasticity. The results of the testing of the properties of the mixtures is set out in Table 2. In each case, in addition to an increase in raw tensile strength, a considerable rise in defo hardness at room temperature is achieved with the level at 80 C. being maintained in the samples containing the polyoctenamer.

TABLE 2 jected to high dynamic stresses, is admixed 0, l0 and 15 parts by weight, respectively, of polydodecenamer (trans-1,4-content RSV 0.5 dl./g.):

Parts Natural rubber, Sheets Defo 1250 50 SBR 1707 41.25 cisl ,4-Polybutadiene 20 FEF [Fast Extruding Furnace] 40 carbon blac Light plasticizer oil 13.75 Zinc oxide 3 Stearic acid 2 Sulfur 3 Vulkacit" CZ 1.3

(N-cyclohexylbenzothiazole sulfenamide) RUBBER RAW DEFO ACC to DIN 53 514 POLYOCTEN- TENSILE ELONGA- AMER STRENGTH TIQN% 20 C. C.

kgJcm 2a Synthetic Polyisoprene (Ziegler Type) None 1.7 132 2000/1 l 700/10 Commercial Product Natsyn" 2200 2b do. 15 Parts 4.0 89 5500/18 600/6 by Wt.

2c Synthetic Polyisoprene Li Type, Commercial None 1.7 2450/13 900/8 Product Cariflex" IR 305 2d do. 15 Parts 3.6 63 5500/15 640/6 by Wt.

2e SBR 1712 None 3.8 104 5750/22 1500/18 2f do. 15 Parts 4.7 119 8250/28 1320/20 by Wt.

2g SBR 1707 None 3.2 177 4500/34 1500/26 2h do. 15 Parts 49 129 7500/32 1400/26 by Wt.

21' cis-1,4-Polybutadiene Commercial None 2.2 367 2400/34 1300/28 Product Buna CB 30 2] do. 15 Parts 7.2 263 4600/37 1300/27 The properties of the elastomeric mixtures and the vulcanizates with and without addition of polydodecenamer are set forth in Table 3. In addition to advan tages in the processing operation for the elastomeric than 4,000, wherein the elastomer therein has a deformation hardness of from 2,000 to 4,000 at 20 C.

6. A vulcanizable elastomeric mixture according to claim 1 having a deformation hardness at 20 C. of

5. A vulcanizable elastomeric mixture according to claim 1 having a deformation hardness at 20 of more mixtures according to this invention as shown by defo from 5,000 to 9,000. wherein the elastomer therein has values at C. and 40 C. and raw tensile Strength, no a deformation hardness of from 2.000 to 4.000 at 20 disadvantageous effects on the vulcanizate results. (1

TABLE 3 Mixture Mixture Mixture Without Polydodecenamer l07r Polydodecenamer lS'Z Polydodccenamer Unvulcanized tensile 2.6 3.9 45

strength (kg. cm)

Mixture defo vulcanization at 143 0. minutes 15' 60' 120' 15' 30' 60' 120' 15' 30' 60' 120' Tensile strength kg./cm"') 1611 145 128 125 162 156 151 135 169 1611 135 128 Eltmgution 544 402 372 380 534 424 418 402 514 436 366 372 Modulus 300 '7:

(kg/cm) 61 92 92 86 66 95 95 88 78 99 101 95 Impact strength according 16 P011! 20 10 9 9 18 12 12 8 18 15- 9 s Hardness Shore Elasticity 20 c. 60 62 62 60 5s 61 61 59 58 62 60 5s Compression set l6 l5 l8 DIN Abrasion (mm") I56 145 I54 Goodrich Flcxometer (AT) ll.5 ll.() ]2 The preceding examples can be repeated with similar 7. A cross-linked vulcanizate of the elastomeric mixsuccess by substituting the generically or specifically ture according to claim 5, having a deformation harddescribed reactants and/or operating conditions of this ness at 20 C. of more than 4,000. invention for those used in the preceding examples. 8. A method of increasing the deformation hardness From the foregoing ip i n, One Skilled in the art of a vulcanizable elastomeric mixture whose elastomer can easily ascertain the essential character1st1cs of th1s h a d f ti h d t 20 C. f l th 6,000, invention. and Without p g from the p and which comprises incorporating therein an amount from Scope thereof, can make VHTIOUS changes and mOdlfiCa- 2-20 percent by weight, based on the elastomer, effections of the invention to adapt it to various usages and i to impart a d f ti h d to h l h meric mixture which is substantially greater than the what 15 claimed 15? deformation hardness of the elastomer, of a polyoctel. vulcanizable elastomeric mixtures comprising an namer, a polydodecenamer or a mixture thereof whose elastomer havmg a deformation hardness of less than double bonds are more than 60 percent in the trans 61090 at and an amount, from 7 pefcem by configuration and which has a reduced viscosity of 0.2 weight, based on the elastomer, effective to impart a 30 dug at deformation hardness to the elastomeric mixture which 9. A method according to claim 8 wherein a I is substantially greater than the deformat1on hardness lyoctenamer having double bonds which are 75 95 pen of the of T g i g i z f cent in the trans-configuration is incorporated therein.

' g f ig z i gsg s fi gg z 5 10. A method according to claim 8 wherein a polydos Sit ofo 2 3 at 6 decenamer having double bonds which are 75-95 perg as are y cent in the trans-configuration is incorporated therein.

Alvulcanlzable sekllsstomenc f i 11. A method according to claim 8 wherein 5-1 5 perclalln comammg p0 yoc i cent of the polyoctenamer, polydodecenamer or mixhavmg double bfmds w are percent e ture thereof is incorporated therein. transconfigur?tlon' 12. A method according to claim 8 wherein the clas- A vulcmllzflble elastomenc mlxturedacgor mg to tomer is selected from the group consisting of natural r 1 comammg 545 Percent Ofa Poly 0 ecerlamer rubber, polyisoprene, styrene-butadiene rubber and having double bonds which are 75-95 percent in the cis l,4 polybutadiene tfans-configur atlon- 13. An article of manufacture comprising an unvul- A vulcamzflble elastomenc {mxture accordmg to canized automobile tire formed of an elastomeric mixclaim 1 wherein the elastomer is selected from the ture according to Claim 5. group consfstmg of natural r polylsopfene 14. An article of manufacture comprising an unvulrene'butad'ene rubber and 4Plybutad1enecanized automobile tire formed of an elastomeric mix- 

2. A vulcanizable elastomeric mixture according to claim 1 containing 5-15 percent of a polyoctenamer having double bonds which are 75-95 percent in the trans-configuration.
 3. A vulcanizable elastomeric mixture according to claim 1 containing 5-15 percent of a polydodecenamer having double bonds which are 75-95 percent in the trans-configuration.
 4. A vulcanizable elastomeric mixture according to claim 1 wherein the elastomer is selected from the group consisting of natural rubber, polyisoprene, styrene-butadiene rubber and cis-1, 4-polybutadiene.
 5. A vulcanizable elastomeric mixture according to claim 1 having a deformation hardness at 20* of more than 4,000, wherein the elastomer therein has a deformation hardness of from 2,000 to 4,000 at 20* C.
 6. A vulcanizable elaStomeric mixture according to claim 1 having a deformation hardness at 20* C. of from 5,000 to 9,000, wherein the elastomer therein has a deformation hardness of from 2,000 to 4,000 at 20* C.
 7. A cross-linked vulcanizate of the elastomeric mixture according to claim 5, having a deformation hardness at 20* C. of more than 4,000.
 8. A method of increasing the deformation hardness of a vulcanizable elastomeric mixture whose elastomer has a deformation hardness at 20* C. of less than 6,000, which comprises incorporating therein an amount from 2-20 percent by weight, based on the elastomer, effective to impart a deformation hardness to the elastomeric mixture which is substantially greater than the deformation hardness of the elastomer, of a polyoctenamer, a polydodecenamer or a mixture thereof, whose double bonds are more than 60 percent in the trans-configuration and which has a reduced viscosity of 0.2 - 3.0 dl./g. at 135* C.
 9. A method according to claim 8 wherein a polyoctenamer having double bonds which are 75-95 percent in the trans-configuration is incorporated therein.
 10. A method according to claim 8 wherein a polydodecenamer having double bonds which are 75-95 percent in the trans-configuration is incorporated therein.
 11. A method according to claim 8 wherein 5-15 percent of the polyoctenamer, polydodecenamer or mixture thereof is incorporated therein.
 12. A method according to claim 8 wherein the elastomer is selected from the group consisting of natural rubber, polyisoprene, styrene-butadiene rubber and cis-1,4-polybutadiene.
 13. An article of manufacture comprising an unvulcanized automobile tire formed of an elastomeric mixture according to claim
 5. 14. An article of manufacture comprising an unvulcanized automobile tire formed of an elastomeric mixture according to claim
 6. 